1. Field of the Invention
The invention relates to a current generator capable of outputting an accurate output current that is insensitive to environment temperature and supply voltages.
2. Description of the Related Art
An output current generated by a conventional current generator depends upon supply voltage, environment temperature as well as process corner and resistance shift of resistor, which, in certain situations, may be unexpected and likely to make the following stage malfunction.
FIG. 1 is a circuit diagram of a conventional current generator. In FIG. 1, the output current la equals (Vgs-Vt)/Ra, where Vgs is the voltage between the gate and the source of the transistor 110, Vt is the thermal voltage of the transistor 110. Since Vgs depends on the supply voltages Vdd/Vss and Vt is sensitive to the environment temperature, the output current la also depends upon the supply voltages and the environment temperature, as well as process corner and resistance shift of the resistor Ra.